Utilization of the service software of an electrical device (e.g., of a medical device) may be restricted to authorized persons. A symmetrical encryption method has been used in which various features of the medical device are combined with a secret. From this, a license key is generated. The secret may be discovered in relevant internet circles, or the license keys may become available on the black market.
Protective methods for preventing or impeding fraud may be used. In the public/private key method based on digital certificates, a handshake or a challenge/response method may be used. The establishment of a public key infrastructure (PKI) has a regular certificate update due to elapsing validities. The input of static key information uses a great length of key in order to reduce brute force attacks. Long key lengths are user-unfriendly. Time based one time passwords have a drawback of presupposing a time synchronization or an on-line connection.